Long Term Evolution (LTE) is a radio technology designed to increase the capacity and speed of mobile communication networks. LTE provides for an end-to-end Internet Protocol (IP) service delivery of media. Currently, LTE comprises a set of enhancements to the Universal Mobile Telecommunications System (UMTS), which is described in a suite of Technical Specifications (TS) developed within and publicized by the 3rd Generation Partnership Project (3GPP).
LTE, in part, provides for a flat IP-based network architecture designed to ensure support for, and mobility between, some legacy or non-3GPP systems such as, for instance, GPRS (general packet radio service) and WiMAX (Worldwide Interoperability for Microwave Access). Some of the main advantages with LTE are high throughput, low latency, plug and play, FDD (frequency-division duplex) and TDD (time-division duplex) in the same platform, improved end user experience, simple architecture resulting in low operating costs, and interoperability with older standard wireless technologies such as GSM (Global Systems for Mobile Communications), cdmaOne™, W-CDMA (UMTS), and CDMA2000®. Many major carriers in the United States (US) and several worldwide carriers have started to convert their networks to LTE.
LTE and other 3GPP compliant systems (meaning systems having elements that operate in compliance with 3GPP TSs) also provide Multimedia Broadcast Multicast Service (MBMS) point-to-multipoint transport of media to user equipment (UE) operating on the system. MBMS operation allows a defined set of LTE cells to “simulcast” bit for bit identical information in a Multicast Broadcast Single Frequency Network (MBSFN). This simulcast of information provides constructive RF interferences over a wide area, improving both coverage and performance when many endpoints desire to receive the same content. A UE can receive MBMS content either in connected mode or idle mode.
Starting in 3GPP release 8, E-MBMS is now referred to as E-MBMS (Evolved MBMS) to distinguish it from previous 3GPP architectures. Similarly, there are changes to the name of the Radio Access Network (RAN), i.e. the UTRAN becomes the E-UTRAN, and the core, i.e. this becomes the Evolved Packet Core (EPC). A multi-cell E-MBMS transmission provides a transmission of bit for bit identical information at exactly the same time and frequency, and is also referred to as an MBSFN transmission (Multicast Broadcast Single Frequency Network transmission). An alternative, generic industry term for such a simulcast transmission is an ‘SFN transmission’, but the term MBSFN transmission will be used henceforth. Cells are configured to belong to a MBSFN Area. All cells that belong to a defined MBSFN area, and which participate in a MBSFN transmission, will transmit E-MBMS media (media content) at exactly the same time and frequency. As a consequence, all cells simulcast bit for bit identical information at exactly the same time and frequency.
Unfortunately, the E-MBMS transport mechanisms that are described in the 3GPP TSs have many shortcomings when applied to mission critical group communications. However, if organizations having more stringent requirements for media transport are going to use 3GPP E-MBMS technology, it is desirable for these systems to provide enhanced coverage and performance.
In 3GPP compliant systems, handover applies to connected mode only UEs, in which the cell mobility event is controlled by the network. On the other hand, cell reselection applies to idle mode UEs, and is performed entirely by the UE. With cell reselection by an idle mode UE, the network is neither involved nor aware.
Accordingly, there is a need for enhancements to Multimedia Broadcast Multicast Services.
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